Filter cartridges are used in many applications, including medical devices. In the medical field, filter cartridges containing certain powdered filter media are used. One application for such a filter cartridge is in a dialysis system.
Systems for patients requiring hemodialysis or peritoneal dialysis can involve pumping a large volume of dialysate through a dialyzing device. In these devices, the used dialysate is generally discarded after a single passing.
More recent embodiments of dialysis devices involve pumping a fixed volume of dialysate through a dialyzing device, whereupon the used dialysate flows through a filter cartridge and is then returned to a dialysate reservoir for reuse. Flow through the cartridge, however, does not optimize filtering of the dialysate through various granular filtering media.
Fluid flows through filter media of varying particle sizes and granular diameters at various rates and pressures. Fluid flows at a higher rate and at a lower pressure through granules of larger diameter. Conversely, fluid flows at a slower rate and at a higher pressure through granules of smaller diameter. The flow of a fluid through a filter cartridge having filter media sections of varying granule diameters takes different directional flow paths through the respective sections. As a result, fluid flow through a powdered medium containing large diameter granules disposed in a filter cartridge is laminar. Fluid flow through a powdered filter medium containing small diameter granules disposed in a filter cartridge is not laminar and results in a condition known as wicking. Wicking occurs when the fluid generally flows in the direction of areas of least pressure which tend to be areas between the inner wall of the tubular housing and the powdered filter medium. Wicking results in the fluid bypassing the majority of the surface area of the granular filter medium. As a result, filtering is inefficient.
A need therefore exists for a filter cartridge assembly that optimizes filtering efficiency of a fluid.